1. Field of the Invention
The present invention relates to a pump hose for a peristaltic pump.
2. Related Art
In the field of medicine, peristaltic pumps or hose pumps are used as infusion pumps. Such pumps allow a sterile transport of larger quantities of an infusion liquid. The replaceable pump hose is a cheap one-way product delivered in a sterile manner that can be inserted into the infusion device by the user and is disposed after use. However, high requirements are to be met by the pump hose concerning flexing properties, elasticity, resistance to abrasion and stability in dimension. The delivery volume depends on the cross-sectional dimensions and on the restoring properties of the pump hose. Further, the material used must be physiologically safe; i.e., it must be inert to the media used. Environmental influences, such as temperature, air humidity, light and disinfectants must not affect the material.
Normally, pump hoses for peristaltic pumps are made of highly elastic material; e.g., silicon, with a high stability in dimension. The pump hose is inserted into the infusion conduit through special connection members that may serve as fastening means. The known pump hoses have a round cross section. If a hose with a round cross section is squeezed by an external force acting on it, a non-uniform strain results on the material with a heavy strain being placed in particular on the kinkings of the hose cross section. The strain on the material is even increased, since the degree of squeezing of the hose not only causes the two hose wall portions to contact each other, but also since an excessive force is applied for effecting a safe squeezing which causes a compression of the hose halves flatly abutting each other. Since such squeezing is often repeated with peristaltic pumps, symptoms of fatigue of the hose material occur. Moreover, there is the danger of abrasion of hose material within the hose, whereby foreign particles may get into the infusion solution. A very strong squeezing of the material occurs on the inner side of the hose at the kinking lines thereof resulting from the hose squeezing, whereas strong extensions occur on the outside. Further, the peristaltic pumps are subjected to tolerances due to which the degree of the squeezing of the hose varies. All these facts lead to a change in the volume of the hose during use, which results in a varied delivery or infusion rate.
A further disadvantage of the known pump hoses is that the hose wall is resilient only to a low degree, due to the required high restoring capacity, and that the measurement of the fluid pressure by means of pressure sensors elastically pressing against the hose wall from outside is made harder. Finally, another disadvantage is represented by the necessity of providing additional fastening means on the pump hose.
A pump hose is known from German Pat. Publication No. 31 12 837 A1, wherein two arcuate portions enclose the hose lumen so that the hose lumen takes the form of an ellipse. Ribs which extend laterally in opposite directions are provided. These ribs serve to position the pump hose within the hose pump. Their thickness is not substantially greater than the wall thickness of the arcuate portions. When squeezing the pump hose, the pressure rollers act exclusively on the arcuate portions that are pressed against each other. There is no pressing or supporting in the area of the ribs.
Besides various other hose forms, U.S. Pat. No. 4,540,350 discloses a pump hose consisting of two sheets laid flatly upon each other and connected along their edges. Thereby, lateral ridges are obtained, the thickness of which is twice the thickness of an arcuate portion. However, this hose is preformed to the squeezed condition. Such a hose has practically no restoring capacity for drawing off liquids. Further, there is a danger of leaking occurring in the area of the connected sheet edges, particularly after a repeated deformation of the hose.
It is an object of the present invention to provide a pump hose in which the local strain on the material during the squeezing is reduced so that damage to the material is avoided and an improved restoring behavior is achieved.